There conventionally exist, for video editions, an approach in which editions are performed on a videotape or film on which video or images have been recorded and an approach in which video or image data recorded on a videotape or film is converted to digital data for editions.
In the case of performing editions on a videotape or film on which video or images have been recorded, it is necessary to perform editions sequentially for a time axis of video or image data that is material (which time axis will be referred to as “material time” hereinafter), while reading temporal information that is called time code. Therefore, the editing operation is linear for the material time. In contrast, video or image data as converted to digital data, if stored in a hard disc or the like of a personal computer, workstation or the like, can be flexibly edited in addition to the playback direction and playback time by accessing the stored video data on a random basis without taking the material time into account. Therefore, the editing operation may be nonlinear for the material time. For this reason, an apparatus for digitally editing video data is also called “nonlinear editing apparatus”. If such a nonlinear editing apparatus is used, then a wide variety of editions can be performed, beyond comparison with the conventional tape editions using videotapes, without having to take the time code into account; for example, if some midway scene becomes unnecessary, the following scenes can be shifted forward.
In the case of using such a nonlinear editing apparatus, encoded video stored, for example, in a hard disc can be read therefrom, decoded, reproduced, and then edited while being viewed by use of a monitor. There conventionally exists a nonlinear video editing apparatus that can reproduce video data, which is to be edited, to allow the starting position (in-point) and ending position (out-point) of a scene, which is to be cut out, to be set at the corresponding positions of the video data, while allowing the video of the video data to be viewed. These in-point and out-point are associated with the video data and held as editing information, and a clip of the scene as cut out is formed based on this editing information. It should be noted that in the nonlinear video edition, there is no need to actually copy or cut any original video data in order to form clips and during a clip playback, a clip is specified, thereby referring to the editing information and decoding and reproducing the video data ranging from the in-point to the out-point.
Some types of nonlinear editing apparatuses can use an editing function, which is called “clip marker”, to place marks at any desired scene positions of the video and audio of a clip. Further, patent literature 1 discloses an editing system wherein an editing function, which is called “time remapping”, is used to flexibly change the playback rate of the video and audio of a clip to any desired rate and display the status of the change in the playback rate on a user interface. The playback rate can be changed by use of, for example, a key frame specified by a user or editor and a set of mathematical expressions of line segment interpolations and Bezier interpolations utilizing the key frame.
According to the conversional method, if video data that is material (which will be referred to as “material data” hereinafter) is subjected to editions including a time remapping conversion process to generate video data to be played back (which will be referred to as “playback data” hereinafter), then it is relatively easy to cause marks placed in the material data and indicating given “positions” on the material time to be reflected in the playback data. However, in a case where marks defining a given “range” on the material time are placed in the material data, if a time remapping conversion from the material time to the playback time is simply applied, the change in the time interval between the starting and ending points of the range is not taken into account, with the result that the range indicated by the marks placed in the material data may not correctly be reflected in the playback data.
FIGS. 1A-1C are graphs showing correspondences of clip markers between the material time and the playback time. In FIGS. 1A-1C, marks placed at given positions of the material data are shown as clip markers a, b, c, d and e. FIG. 1A illustrates a case where a playback time is set such that a playback is performed at the same playback rate as the material time. In the example of FIG. 1A, as shown by solid lines, there exit only single playback times a′ and b′ that correspond to the clip markers a and b of the material time, respectively, while as shown by dotted lines, there also exit only the single material times a and b that correspond to the playback times a′ and b′, respectively. FIG. 1B illustrates a case where a playback time is set such that a playback is performed with the playback rate of the material time varied. In the example of FIG. 1B, as shown by solid lines, for example, there exist a plurality of playback times d1′, d2′ and d3′ corresponding to the material time denoted by the clip marker d. FIG. 1C illustrates another case where a playback time is set such that a playback is performed with the playback rate of the material time varied. In the example of FIG. 1C, there exists no playback time that corresponds to the material time denoted by the clip marker e. However, even in such a case, there necessarily exits a single material time corresponding to a time of the playback time denoted by, for example, f.
In the case where the material time is the same as the playback time (FIG. 1A), the positions of the playback time correspond to the respective positions of the material time in a one-to-one relationship. In contrast, in the cases where the playback time is set such that the playback is performed with the playback rate of the material time varied as shown in FIGS. 1B and 1C, there may exist a plurality of playback times corresponding to the position of a material time, or no playback time may exit that corresponds to the position of a material time.
As previously stated, in a case where clip markers are used to define a given “range” of the material data and then a time remapping conversion from the material time to the playback time is simply applied, the change in the time interval between the starting and ending points of the range is not taken into account, with the result that the range defined by the clip markers placed in the material data may not correctly be reflected in the playback data. For example, in a case where a range is specified in such a manner that the clip marker d shown in FIG. 1B serves as the starting or ending point of the specified range, the corresponding playback times d1′, d2′ and d3′ can be known indeed but the time change between d1′ and d2′ and the time change between d2′ and d3′ are not taken into account. For this reason, it cannot be determined whether or not the ranges between d1′ and d2′ and between d2′ and d3′ in the playback time correspond to the range specified in the material time.
Therefore, in a case where the material data is a recorded data of, for example, the TV broadcast of a succor game and a range of a goal scene in the game is specified by use of clip markers, even if the goal scene as specified by use of the clip markers is to be played back, by use of the playback data, after a time remapping conversion process, then it cannot correctly be determined to which range of the playback data as subjected to the time remapping conversion process the range of the goal scene as specified in the material data corresponds, with the result that only a portion of the goal scene may be played back or the goal scene may not be appropriately played back.
Thus, according to the conventional art, it was possible to determine the mutual correspondence between any given “position” in the material data and a “position” at which the given position is reflected in the playback data as subjected to a time remapping conversion process. However, it was difficult to determine the mutual correspondence between any given “range” specified in the material data and a “range” in which the given range specified in the material data is reflected in the playback data as subjected to a time remapping conversion process.